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.\" Portions of this software were developed by Ka Ho Ng
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.Dd April 8, 2021
.Dt VNODE_PAGER_SETSIZE 9
.Os
.Sh NAME
.Nm vnode_pager_setsize
.Nd "notify the VM system about updates in the file size"
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/vm_extern.h
.Ft void
.Fn vnode_pager_setsize "struct vnode *vp" "vm_ooffset_t nsize"
.Sh DESCRIPTION
.Nm
lets the VM system know about a change in size for a file,
and updates the object size and vnode pager size of the vm object in
.Fa vp
with
.Fa nsize .
Page faults on the object mapping with offset beyond the new object
size results in
.Va SIGBUS .
.Pp
Pages between the old EOF and the new EOF are removed from the object queue
if the file size shrinks.
In case the new EOF specified by the
.Fa nsize
argument is not aligned to page boundary,
partial-page area starting beyond the EOF is zeroed and marked invalid.
if the page exists resident.
.Pp
In case the vnode
.Fa vp
does not have a VM object allocated, the effect of calling this function is no-op.
.Pp
This function must be used within file system code to implement truncation
if the file system allocates vm objects for vnodes.
.Sh LOCKS
The vnode should be exclusively locked on entry and will still be locked on exit.
.Sh SEE ALSO
.Xr vnode 9
.Sh HISTORY
The
.Nm
manual page first appeared in
.Fx 14 .
.Sh AUTHORS
This
manual page was written by
.An Ka Ho Ng Aq Mt khng@FreeBSD.org .
